Kabindra Raj Bhattarai, Ph.D. Scholar
Vivekanada Global University, India
Abstract:
Carboxylated polysulphones have been prepared through metalized intermediate by the reaction of THF solution of polymer with n-butyllithium and then treatment with carbon dioxide. In this reaction, there was no requirement of tertiary amine catalyst. A series of reaction have been done in the salt, acid and ester form. The structure of the polymer and its derivatives were characterized by using proton-NMR, carbon-13-NMR and also IR.
Introduction:
Polysulphone is a widely used thermoplastic for the synthetic membranes particularly in ultrafiltration processes and as porous backing supports for thin film composite. It is thermally and chemically stable. It also has mechanical strength. Due to its hydrophobic nature it has aqueous membrane applications too.
However, Himeshima and Kurihara have been prepared hydrophilic carboxylated polymers from polysulphone by a two-step process of acetylation and bromoform reaction. The direct lithiation / carboxylation reaction has been employed in the modification of the other polymers.
Experimental:
Materials and methods:
Anhydrous reagent grade of tetrahydrofuran (THF) was used. The polymer solutions were prepared in previous day in glassware that had been dried overnight at 120 °C.
Polymer synthesis:
A solution of polysulphone (221g; 0.50 mol) in THF (1900 ml) was cooled to -50 °C by immersion in a dry-ice / alcohol bath. N-bulyllithium (40ml, 0.40 mol) was injected dropwise at the rate of about 30 ml using a syringe pump. This mixture initiating turned green, then developed a red-brown coloration and became very viscous. The solution was stirred for 15 minutes. Then freshly prepared
was added to the litherated polysulphone and it was mixed vigorously. This was left overnight to warm to the room temperature. The residual THF was separated out. Carboxylated polymer was recovered by agitating the precipitate with ethanol.
Structure determination:
Proton-NMR and Carbon-13-NMR spectra were recorded on a Bruker AM-400 spectrometer at room temperature. Carbon-13-NMR spectra were recorded with proton noise decoupling. Polymers were dissolved in with an internal tetramethylsilane (TMS) standard. Proton-NMR spectral data and elemental analysis for the polymers were obtained.
Polymer Characterization:
IR measurements were made on a Perkin-Elmer 1500 pectrometer. IR sample in the form of films of thickness about 0.001 in were cast on to the glass plate from 10% polymer solutions.
Result and Discussion:
Synthesis:
A series of carboxylated polysulphones with degree of substitutionbetween 0.29 and 1.90 groups per repeat unit were prepared. Polysulfone was lithiated at reduced temperature in THF using various ratios of n-butyllithium to polymer. Reduced temperature was necessary to prevent crosslinking of the intermediates.
Proton-NMR, Carbon-13-NMR and IR has been performed for structure characterization of polymer. The thermal stability of the polymers was measured by thermogravimetry. Similarly, water absorption measurements were conducted by immersing dense films prepared from evaporated solutions.
Conclusions:
A series of carboxylated polysulphones with ranging from 0.29 to 1.90 groups per repeat unit were prepared by lithiation/carboxylation modification procedure. Reduced temperature was necessary during the lithiation step to prevent crosslinking. Structural analysis by proton-NMR and carbon-13-NMR analysis were used for structural analysis.
References:
- Michael D. Guiver, S. Croteau, John D. Hazlette and O. Kutowy, British polymer Journal 23(1990) 29-39.
- Noshay A. and Robeson L. M., J. Appl. Polym. Sci., 20 (1976) 1885.
- Himeshima Y. and Kurihara M.,Jpn Kokai Tokyo Koho 88101425 (6 May 1988).
